1. Field of the Disclosure
The present disclosure is in the field of methyl perfluoroheptene ether compositions. These compositions are zero ODP, low GWP compositions and are useful in precision cleaning applications as a defluxing agent and for removing oils or residues from a surface.
2. Description of the Related Art
Precision cleaning is required throughout a broad range of modern industries. Industries as diverse as printed circuit board manufacturing and watchmaking require cleaning to stringent standards to ensure the final product provides reliable and trouble-free performance. A vast array of industries, including the aerospace, transportation, telecommunications and data processing industries all employ critical electronics and circuit boards whose failure can be catastrophic. The printed circuit boards (PCBs) employed in these systems must be cleaned with a solvent prior to their use to remove flux and other soils introduced during the PCB manufacturing process. Products used in the semiconductor industry require precision cleaning to meet stringent performance criteria. The aerospace industry requires precision cleaning of landing gear to eliminate fracturing of landing gear parts due to trapped water. The jewelry and watchmaking industries demand an end product that is aesthetically pleasing, spot-free and void of any soils. Medical devices ranging from surgical needles to artificial heart valves must be cleaned to stringent standards to prevent infection and the spread of disease. The automotive industry requires precision cleaning of critical parts such as fuel injectors, ABS brakes, compressors, relays, sensors and switches. Solvents are also required for the spot-free cleaning of optical parts including optical assemblies, lenses, fiber optics and flat-panel displays.
Precision solvents should ideally be nonflammable and have low toxicity to provide safety in use. High solvent effectiveness at removing soils is also desired. Solvent effectiveness is typically expressed as a Kauri Butanol (KB) value, which reflects the ability of the solvent to dissolve heavy hydrocarbon greases—the higher the KB value, the higher the effectiveness of the solvent.
During the early 1970s, the most popular solvent for precision cleaning was trichloroethylene (TCE). Due to environmental issues related to water and ground pollution, however, TCE was replaced in many applications by the fluorine-based solvent CFC-113 beginning in the late 1970s. TCE continues to face increasing regulations, both domestically and abroad, and is also a potential carcinogen. CFC-113, however, is, a solvent which contributes to the destruction of stratospheric ozone and is characterized by a large ozone depletion potential (ODP value). As a result CFC-113 has since been banned due to its ozone depleting properties under the provisions of the 1987 Montreal Protocol. Following the ban of CFC-113, solvents with low, but not zero ODPs were developed, including solvents such as HCFC-141b and HCFC-225. However, these solvents are scheduled for phaseout in the near future due to their ozone depleting characteristics. More recently, zero ODP solvents have been developed, including hydrofluorocarbons (HFCs) and hydrofluoroethers (HFEs). Although these compounds do not contribute to ozone depletion, they are characterized by moderate global warming potentials (GWPs) and are classified as Greenhouse Gases (GHGs), i.e., gases which contribute in some degree to global warming/climate change. Among HFCs which have been found useful for precision solvent applications include 1,1,1,2,3,4,4,5,5,5-decafluoropentane (HFC-43-10mee), known commercially as Vertrel XF. Azeotropic compositions comprising about 58-68 weight percent 1,1,1,2,3,4,4,5,5,5-decafluoropentane (HFC-43-10mee) and about 32-42 weight percent trans-1,2-dichloroethylene are described in U.S. Pat. No. 5,196,137.
Azeotropic compositions comprising from 0.4 to 29 weight percent MPHE and trans-1,2-dichloroethylene are disclosed in U.S. Pat. No. 8,410,039. Compositions comprising 13.5 weight percent MPHE and 86.5 weight percent trans-1,2-dichloroethylene are not sufficiently nonflammable to be used in some solvent cleaning applications. When such compositions are tested for flash point according to ASTM D56-05, they exhibited some flashes when tested in multiple replicates indicating the potential for some flammability under some conditions.
It is obvious there is a need for precision solvents that are not only characterized by low toxicity, and high solvency, but are also characterized by zero ODPs and low GWPs. Even more desirable are solvents that are also nonflammable.
The present disclosure provides zero ODP, low GWP compositions useful in precision cleaning applications such as semiconductor chip and circuit board cleaning, defluxing, and degreasing processes. The present compositions are also characterized by high solvency power and low toxicity.